Hi,
From the sounds of what you are seeing this is a windows problem. Not specific for Fusion even while that may seem so for you.
When you delete files on the windows end, there's nothing that Fusion is supposed to do to release the space. It is windows itself that takes care of that.
Disk Cleanup however sometimes does the actual cleaning on first boot. So you get rid of several Gigs, but it doesn't show yet at all.
That's Windows.. does the same thing on physical machines as well.
To actually regain that "cleaned up" space you have to reboot the Windows 7 machine and it starts cleaning.
After you have logged in the space you gained should be visible.
Fusion cleanup is to regain the space your deleted windows files hold on the OS X side in the case your virtual disk is set as type "growing" (the default).
Eg. you delete a 1GB video in Windows.. Windows marks the file as deleted, but it leaves the actual data sitting there. As a result Fusion doesn't reclaim that 1GB extra space on OS X. On the windows side that 1GB is available to be re-used.
Fusion cleanup blanks out deleted file with zero's and then gives that space back to OS X (so you gain 1GB in OS X)
"Windows created a temporary paging file on your computer because of a problem that occurred with your paging file configuration when you started your computer. The total paging size for all disk drives may be somewhat larger than the size you specified."
So you delete files and gain space on the disk which then gets used by the paging file.
You might work around that by assigning more RAM to your virtual machine as a page file will be created (and growing) when your Windows runs out of free memory to use.
--
Wil